tests: hil: ota: wait for successful status report

[sam-golioth]

Previously, the test script was waiting on a string printed by the device before it reports it status, then waiting for a specific delay before retrieiving the reported status from the backend. Instead, the test script now waits for a string that is printed by the device after it receives an acknowledgement from the server that the status update has been posted successfully. This makes the timing of the test more explicit and should reduce timing related failures in CI.

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Code Coverage

Type	Coverage
lines	58.6% (1266 of 2159 lines)
functions	65.3% (126 of 193 functions)